<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        //先执行同步，再执行异步（回调函数）
        console.log(100);
        setTimeout(function() {
            console.log(300);
        }, 0);
        console.log(200);
        console.log(200);
        console.log(200);
        console.log(200);
        console.log(200);
    </script>
</body>

</html>